tracing: protect reader of cmdline output
Impact: fix to one cause of incorrect comm outputs in trace
The spinlock only protected the creation of a comm <=> pid pair.
But it was possible that a reader could look up a pid, and get the
wrong comm because it had no locking.
This also required changing trace_find_cmdline to copy the comm cache
and not just send back a pointer to it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 4c38860..6004cca 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -190,15 +190,15 @@
static enum print_line_t
print_graph_proc(struct trace_seq *s, pid_t pid)
{
- int i;
- int ret;
- int len;
- char comm[8];
- int spaces = 0;
+ char comm[TASK_COMM_LEN];
/* sign + log10(MAX_INT) + '\0' */
char pid_str[11];
+ int spaces = 0;
+ int ret;
+ int len;
+ int i;
- strncpy(comm, trace_find_cmdline(pid), 7);
+ trace_find_cmdline(pid, comm);
comm[7] = '\0';
sprintf(pid_str, "%d", pid);